Gas burner structure



Feb. 5, 1963 w. E. ROBB 3,076,497 GAS BURNER STRUCTURE Filed NOV. 17, 1958 FIG. 3

INVENTOR W. E. ROBB BY/L41%WM ATTORNEY United States Patent Ofiflce 3,076,497 Patented Feb. 5, 1963 3,076,497 GAS BURNER STRUCTURE Wendell E. Robb, Winfield, Kans., assignor to Gordon & Pratt, lnc., Winfield, Kans., a corporation of Kansas Filed Nov. 17, 1958, Ser. No. 774,453 3 Claims. (Cl. 158-109) This invention relates to heating. In a more specific aspect, this invention relates to heating means. In a still more specific aspect, this invention relates to new burner structure. Still a more specific aspect of this invention relates to new burner structure for fuel gas. In yet a more specific aspect, this invention relates to new fuel gas burner structure for furnaces, particularly furnaces for heating boilers, wherein the new burner of the invention is mounted for use in thewall of 'the furnace, and wherein primary or initial combustion of fuel gas is carried on in a remotely located and protected initial primary combustion zone away from furnace chamber heating zone turbulence and secondary combustion air turbulence, particularly at-the inlet thereof into the furnace chamber.

Fuel gas burners have long been known in the art, such being commonly used to mix fuel gas and combustion air or other oxygen-containing gas for burning the fuel gas in heating relation in the furnace chamber of a furnace. Almost all of the burner structures of the prior art provide for introduction into the furnace chamber of what is commonly referred to as secondary combustion air or other .oxygenrcontaining gas, for secondary combustion or further combustion of the fuel gas in the furnace and away from thevicinity of the fuel gas flame, whichis normally located adjacent toand at the outlet of the usual fuel gas orifices or ports of introduction of fuel gas. It is usual to make no separate introduction of primary and secondary combustion air. Combustion air turbulence in the furnace chamber is desirable from the standpoint of mixing fuel gas and combustion air to result in high efliciency. However, in the usual and common prior art burner such turbulence must be held to a low andineflicient level due to the lack of flame stability and/or the presence of combustion pulsation, which is very undesirable. The burners of the prior art are not easy to adjust for varying conditions of furnace firebox size, shape, pressure, and the like, and the usual and com; mon burner cannot handle a wide range of fuel gas rates, or wide range of gas-air ratios without a great deal of difliculty. Chief among the disadvantages of the burners of the prior art, is the frequent flame blow out, making for unreliable and unsafe burner and furnace operating conditions.

The new burner of my invention formixing fuel gas and oxygen-containing gas, preferably air, and burning the fuel gas has means to deliver the oxygen-containing gas employed in combustion to burn the fuel gas. This duct or conduit delivery means for the oxygen-containing gas has an inlet to receive samefrom such a blower means, and an outlet to deliver oxygen-containing gas to a heating zone, for example, the furnace chamber of a boiler. The burner has a primary combustion chamber having a com bustion zone for .the fuel gas therein. This combustion zone within the primary combustion chamber is removed from the outlet of the delivery duct or conduit for the oxygen-containing gas. The burner is equipped with means to deliver fuel gas and oxygen-containing gas to the primary combustion chamber means. The new burner of my invention is constructed and operable to primarily burn the fuel gas in the primary combustion chamber, preferably in the combustion zone therein which is removed from the outlet of the oxygen-containing gas delivery duct or conduit means, and upon such primary burning to discharge resulting partially combusted fuel gas into the heating zone for mixing same with additional 2 oxygen-containing gas which has been discharged into the heating zone from the delivery means for the oxygencontaining gas, and in the heating zone further combustion of the fuel gas is accomplished. In a preferred specific embodiment of the new burner structure of my invention, the oxygen-containing gas duct or conduit delivery means supplies both primary oxygen-containing gas to the combustion chamber of the burner, and. the secondary oxygen-containing gas for secondary combustion in the heating zone, and the duct or conduit means for the oxygen-containing gas forms with a housing for the burner, the primary combustion chamber. having a primary combustion zone therein, such primary combustion chamber being recessed.

The new burner structure of my invention has proven very advantageous in actual use, overcoming the many disadvantages of the burners of the prior art. Great and reliable flame stability results from the new burner of my invention, and in use my new burner will operate for prolonged periods of time undergreatly. varying conditions and over wide ranges of fuel gas-combustion air ratios, without any combustion pulsation occurring in the furnace chamber. With the new burner of my invention, high turbulence of premixed fuelgas and combustion air for initial or primary combustion can be had ,under ideal conditions for flame starting and maintenance during the heating operation. Almost unlimited heating chamber or zone turbulence in the furnace can be made without blowing out the flame of the burner. It has been found that a very Wide range of inputfuel gas rates can be used with the new burner of my invention, and extremely good fuel gas-combustion air ratios can be used for maximum heating efficiency, and this great advantage has been encountered with all rates of fuel gas input. ,The new burner structurefof my invention can be used with a very wide range of fuel gas richness, and with any kind of fuel gas. The preferred specific embodiments of the new burner structure of my invention are very adjustable for differences encountered in furnace firebox size, the shape of the furnace firebox, and the operating pressures of burning existing in the firebox, etc. p g

The main structural feature of the new burnerstructure of my invention which gives rise to the excellent results in operation from the use of my new burner structure, is the recessed initial or primary combustion chamber or zone for the fuel gas, such recessed combustion chamher or zone resulting from the burner structure to protect the initial or primary burner flame. The flexibility and reliability of the new burner of my invention comes principally as a result of this structure. The new burner structure gives initial or primary combustion of the fuel gas in this recessed combustion chamber or zone having an initial or primary burning zone therein removed from the furnace chamber or heating zone therein, and this initial combustion chamber or zone is removed from the point of introduction into the furnace chamber of the usually great quantity of combustion air, which is commonly referredto as the secondary combustion air.

I It is an object of this invention to provide new burning method and means. 1

It is another object of this invention to provide new fuel gas burner structure.

Still another object of this invention is to provide new burner structure for initial or primary combustion of fuel gas remotely of and protected from the heating zone and turbulence therein, and remotely from and protected from secondary combustion air or other oxygen-containing gas introduced into the heating zone by means of the burner structure.

Still a more specific object of this invention is to provide new burner structure for fuel gas, and for mounting inthe wall of a furnace chamber, such new fuel gas burning structure providing for pre-mixing fuel gas and initial primary combustion air, primarily burning such fuel gas and introducing resulting products of combustion into the furnace chamber, and such new burner structure also providing for introducing secondary combustion air into the furnace chamber for further combustion of the fuel gas therein.

It is yet another object of this invention to provide new burner structure for furnace chambers to mix fuel gas and combustion air for burning of the fuel gas initially in the burner and secondarily in the furnace chamber, such new burner structure resulting in great flame stability over a very wide range of fuel gas to combustion air ratios, and with the new burner structure being easily and highly adjustable to different conditions of burning operation.

Other objects and advantages of the new burner structure of my invention will become apparent to those skilled in the art upon reading this disclosure.

Drawings accompany and are a part of this disclosure. These drawings depict preferred specific embodiments of the new burner structure of my invention, and it is to be understood that such drawings are not to unduly limit the scope of my invention.

In the drawings,

FIG. 1 is a partial longitudinal cross section view, partly cut away, of a preferred specific embodiment of burner structure of my invention.

FIG. 2 is a full front elevation view of the burner structure of FIG. 1.

FIG. 3 is a reduced side elevation view, partly in cross section, of the burner structure of FIGS. 1 and 2 shown mounted in the wall of a furnace chamber.

Following is a discussion and description of the new burner structure of my invention made with reference to the drawings whereon the same reference numerals are used to indicate the same or similar parts and/or assemblies. This discussion and description is of preferred specific embodiments of the new burner structure of my invention, and it is to be understood that such is not to unduly limit the scope of my invention.

In operation the burner 5 of my invention mixes fuel gas and combustion air and burns the fuel gas in heating relation to-a furnace chamber 7 wherein burner 5 is commonly mounted for use. The burner 5 has a circular burner housing 9, preferably made of steel or other suitable metal, and this housing 9 has a circular flange 11 therewith, which is constructed to mount the burner in the wall 13 of the furnace chamber 7 (FIG. 3). The flange 11 is preferably provided with apertures 15 for mounting the burner in wall 13 of the furnace chamber. Nuts and bolts (not shown) have been found suitable for such mounting of burner 5 in wall 13.

Circular combustion air conduit or duct means is mounted within burner housing 9 and preferably concentrically mounted within burner housing 9, this air conduit or duct means passing through the burner housing 9 and constructed to receive combustion air in an inlet portion and discharge secondary combustion air into the furnace chamber 7 from an outlet end portion of the air conduit means. The circular outlet end portion 17 of this air conduit or duct is preferably equipped with a choke ring 19, preferably and conveniently made of stainless stcel, and this choke ring has been found desirable and preferable to give high turbulence to secondary combustion, air which passes into furnace chamber 7 from out of this outlet end portion 17 of the combustion air conduit-having choke ring 19 aflixed thereto in a suitable manner. Of course, the outlet end portion 17 can be formed with an outer choke section or portion, if desired.

In the specific embodiment of burner shown in the drawings, fuel oil injection andburning means are shown mounted centrally of the burner. This has been shown in the drawings, because the most desirable burner structures used in practice today provide for both burning of fuel gas and fuel oil. The fuel oil nozzle 21, oil ignition electrode 23, fuel oil supply line 25, and the mounting means therefor shown in the drawings are common to the prior art, and form no part of my invention. However, one skilled in the art can readily see, that in combination, the new burner structure of my invention is particularly valuable from a practical standpoint, because fuel oil burning means can easily be incorporated therein, while still providing for primary or initial combust on of fuel gas in the recessed primary or initial combustion chamber or zone, such being removed from the point of delivery of secondary combustion air. I

in the specific burner structure of the drawings, air spinners or baffies 27 are mounted in a suitable manner between outlet end portion 17 of the air conduit and the mounting assembly for the fuel oil burner equipment, such spinners or baffies 27 giving a swirling motion to secondary combustion air supplied to and delivered from outlet end portion 17 of the combustion air conduit.

The new burner structure of my invention is formed with a recessed primary or initial combustion zone or chamber for the fuel gas. In the preferred specific embodiment of the drawings, this recessed combustion chamber is formed by burner housing 9, outlet end portion 17 of the combustion air conduit having choke ring 19, and a rear wall 29 for the recessed combustion chamber between the burner housing and the outlet end portion 17 of the combustion air conduit. It is preferable as shown to line the burner housing 9 with a refractory ring 31 of ceramic material. Also, the rear wall 29 of the primary combustion chamber is additionally covered with refractory material 33. While I have found It desirable to use the heat insulating refractory materials 31 and 33 to protect the preferably metal portions of the burner structure and to provide refractory sides for the combustion chamber to promote combustion upon the refractory material becoming incandescent during operation and fuel gas burning, it has been found unnecessary in many instances to so line and protect the burner with the refractory material. The recessed annular primary combustion chamber can satisfactorily be formed using only a heat resistant metal portion 9, and an inner heat resistant metal side 17, and a rear wall 29 of heat resistant material wherein are formed the ports for passage for fuel gas and combustion air into the primary combustion chamber. An all steel burner has been produced and successfully operated with no refractory lining to heat protect the metal. Further, in this regard, it has been observed in operation that the burner structure as shown in the drawings provides for a well protected primary or initial combustion of fuel gas from a standpoint of the cooling effect of the secondary combustion air passed through the combustion air conduit directly adjacent the primary combustion zone.

In the burner structure of the drawings, a plurality of fuel gas and primary combustion air ports 35 are mounted in spaced relation in the rear wall 29 of the primary combustion chamber. These are preferably made of metal, suitably mounted in wall 29, and surrounded and heat shielded in the primary combustion chamber by refractory liners- 31 and 33.

To supply primary or initial combustion air for mixing with fuel gas for in turn supplying the combustion mixture to the annular recessed primary combustion chamber, an annular primary combustion air chamber is formed to the rear of the recessed primary combustion chamber by a middle portion of housing 9 to the rear of flange 11, annular wall 29, and a wall 37 formed in a suitable manner between housing 9 and an intermediate portion 39 of the combustion air conduit or duct means which is centrally located in the burner. Within portion 39 of the combustion air conduit or duct means, a primary combustion air adjuster valve 41 is slidably mounted, this adjuster 41 being operable when slid foradv-6,49%

. ward to close the Communicating passageway between the annular primary air chamber and the combustion air conduit. This provides means whereby the amount of primary combustion air can be varied over a wide range The adjuster in FIG. 1 is in almost wide open position.

Apluraliy of fuel gas orifice members Mare-mounted in a suitable manner and in spaced relation in the rear wall 37 of the primary combustion air chamber, one orifice member 43 for each of the ports 35'. These fuel gas orifice members 43 are positioned to deliver fuel gas to the ports 35 and thus the recessed primary combustion chamber, and in such delivery the orifice members 43, primary combustion air chamber and ports 35 operate to mix fuel gas and primary combustion air for burning in the recessed primary or initial combustion chamber, the mixing taking place essentially in the ports 35. h

The rear end portion of burner housing 9, annular wall 37, intermediate portion 39 of the combustion air conduit, and an annular rear wall 45 suitably mounted between housing 9 and combustion air conduit 52, forms an annular fuel gas manifold which is in flow communication with the fuel gas orifice members 43 mounted in the front wall 37 of the gas manifold, Usual conduit means (not:shown), preferably valved, is used to deliver fuel gas to the gas manifold. A pressure gauge 47 is preferably used to indicate gas pressure on the manifold. Thus, with a fuel gas supply pressure indicated by gauge 41' 7,-anda wide adjustment of primary air to the primary air chamber from the combustion air conduit by valve 41 operated by. adjuster .49 to slide valve 41 back andforth, the new burner structure of my invention gives great QOntrol and variation over the gas-air ratio supplied to the recessed primary combustion chamber through ports 35, and of course, such structure affords wide control over the amount of the combustion air delivered as secondary combustion air through and out end portion 17 of the air conduit having choke ring 19 therearound.

The rear portion of the combustion air conduit 52 extends to the housing 54 for blower means (not shown), powered by motor 56 (FIG. 3). The combustion control panel 58 of common design and function is conveniently mounted on the housing for the combustion air supplying means, as is the usual ignition transformer means 60 (FIG. 3).

The greatly important structural feature of the new burner structure of my invention is the recessed primary combustion chamber. Pilot burner 63 is mounted to operate in the recessed primary or initial combustion chamber where the pilot flame is highly protected from furnace chamber turbulence, and protected from secondary combustion air exiting from the outlet end of the combustion air conduit. Little or no failure of pilot flame has been encountered in the use of my new burner stnucture. The pilot box 65 therefor is mounted conveniently on the rearwardly extending portion 52 of the combustion air conduit. The gas pilot flame rod 67 projects outwardly from the burner structure into the furnace chamber, and it is of the usual and common kind.

The preferred specific burner structure of my invention depicted in the drawings is preferably mounted in the furnace (FIG. 3) by surrounding the burner housing 9 with a refractory ring 70. The furnace structure is of a usual and common kind having a main flue 72, and outlets 74 thereto from the furnace chamber 7. The burner installation shown is for a typical scotch marine boiler.

In operation the combustion air is supplied to the burner proper of my invention through duct 52 and burner proper portion 39 thereof. Slide valve 41 is employed to regulate the amount of this combustion air going to the annular primary air chamber and thus to the recessed primary combustion chamber through ports 35 in mixture with fuel gas from orifice members 43. The remainder of the combustion air passes through spinners or baffles, 27, and exits in a swirling motion through outlets 17 and 19' into the furnace chamber 7, whereit functions as secondary combustion air to further combustion of the fuel gas passing into furnace chamber 7 from the primary recessed combustion chamber. As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, inl the light of this disclosure and discussion, without departing from the spirit or the scope of the disclosure or from the scope of the claims.

I claim:

1, A burner for mixing fuel gas and air and burning saidfuel gas in heating relation to a furnace chamber, comprising, in'combination, a circular burner housing, constructed tofbe mounted in the wall of said furnace chamber, circular combustion air conduit means mounted concentrically in said burner housing and therethrough and constructed to receive combustion air in an inlet end portion and discharge secondary combustion air into said air conduit means, said combustion chamber being free of fluid flow constriction between the inlet'and said outletthereof, said wall having'an integral annular outwardly projecting flange portion having a plurality of spaced holes therein to mount said burner in a furnace wallof said furnace chamber with said outlet of said combustion chamber opening directly into said furnace chamher, a plurality of fuel gas and primary combustion air ports in spaced relation in said'wall, a second wall between said housing and saidconduit' means positioned upstream of said tfirst wall, an annular primary air chamber formed by said housing, said air conduit means, said first walland said second wall,-said primary air chamber being in air flow. communication. with said air conduit means, valve meanshaving a sliding member mounted in said air conduit means and positioned and operable'to vary the size of saidpassageway betweensaid primary air chamber and said air conduitnieans, a plurality of fuel gas orifice members mounted in spaced relation in said second wall one for each of said ports and in combustion air mixing relation thereto and positioned to deliver fuel gas to said primary combustion chamber in admixture with combustion air, a third wall between said housing and said conduit means and positioned upstream of said second wall, an annular fuel gas manifold formed by said housing, said air conduit means, said second wall and said third wall, said manifold being in fluid communication with said orifice members, means to deliver combustion air to said air conduit means, and said burner constructed and operable to primarily burn said fuel gas in said recessed primary combustion chamber in a zone therein removed from the outlet of said air conduit means and to discharge partially combusted fuel gas directly into said furnace chamber for mixing same with secondary air and further combustion.

2. A burner for mixing fuel gas and air and burning said fuel gas in heating relation to a furnace chamber, comprising, in combination, a burner housing having means therewith constructed to mount said burner in said furnace chamber, air conduit means mounted in said burner housing and therethrough and constructed to receive combustion air in an inlet portion and dischange secondary combustion air into said furnace chamber in an outlet end portion, a wall between said housing and said air conduit means positioned upstream from said outlet end portion of said air conduit means, said outlet end portion of said air conduit means, said housing and said wall therebetween forming a recessed primary combustion chamber having the outlet thereof at said outlet end portion of said air conduit means, said primary combustion chamber being free of fluid flow constriction between the inlet and said outlet thereof, said housing having an outwardly projecting flange having at least one opening therein to mount said burner in a furnace wall of said furnace chamber with said outlet of said combustion chamber opening directly into said furnace chamber,

fuel gas and combustion air ports in said wall, a second wall between said housing and said conduit means positioned upstream of said first wall, an air chamber formed by said housing, said air conduit means, said first wall and said second wall, an air passageway between said air conduit means and said air chamber, valve means mounted relative to said air conduit means positioned and operable to vary the size of said air passageway between said air chamber and said air conduit means, fuel gas orifice members mounted in said second Wall in operating relation to said ports in said first-named wall in combustion air mixing relation thereto, said fuel gas orifice members positioned to deliver fuel gas to said combustion chamber in admixture with combustion air, a third wall between said housing and said air conduit means and positioned upstream of said second wall, a fuel gas manifold formed by said housing, said air conduit means, said second wall and said third wall, said manifold in communication with said orifice members, means to deliver combustion air to said air conduit means, and said burner constructed and operable to burn fuel gas in said combustion chamber of said burner in a zone therein removed from the outlet of said air conduit means and to discharge partially combusted fuel gas into said furnace chamber for mixing same with secondary air and further combustion.

3. A burner for mixing fuel gas and oxygen containing gas and burning said fuel gas in heating relation to a furnace chamber, comprising, in combination, a burner housing constructed to be mountable in said furnace chamber, oxygen containing gas conduit means mounted in said housing and extending therethrough and constructed to receive oxygen containing gas in an inlet portion and when mounted'in heating relation to said furnace chamber discharge a portion of said oxygen containing gas into said furnace chamber from an outlet end portion for secondary combustion, wall means positioned between said housing and said oxygen containing gas conduit means upstream from said outlet end portion of said oxygen containing gas conduit means and forming with said housing and said oxygen containing gas conduit means a recessed primary combustion chamber with the outlet thereof at said outlet end-portion of said oxygen containing gas conduit means, said primary combustion chamber being free of fluid flow constriction between the inlet and said outlet thereof, ports in said wall means, second wall means positioned between said housing and said oxygen containing gas conduit means upstream of said first-named wall means and defining with said firstnamed wall means, said housing and said oxygen containing gas conduit means, an air chamber, a passageway between said oxygen containing gas conduit means and said air chamber, valve means mounted relative to said oxygen containing gas conduit means positioned and operable to vary the size of said passageway between said air chamber and said oxygen containing gas conduit means, third wall means between said housing and said air conduit means positioned upstream of second wall means and defining with said second wall means, said housing and said oxygen containing gas conduit means, gas manifold means, said second wall means having means therewith in communication with said gas manifold means to pass fuel gas therethrough to said air chamber to be delivered to said primary combustion chamber through said ports in said first-named wall means, and means with said inlet portion of said oxygen containing gas conduit means to deliver oxygen containing gas thereto, said burner being constructed and operable to burn fuel gas in said combustion chamber of said burner in a zone therein removed from said outlet of said oxygen containing gas conduit means and to discharge partially combusted fuel gas into said furnace chamber for mixing with secondary oxygen containing gas and further combustion in said furnace chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,808,319 Roberts June 2, 1931 1,893,533 Barber Jan. 10, 1933 2,220,572 Knupp Nov.5, 1940 2,806,516 Brola Sept. 17, 1957 2,828,609 Ogilvie Apr. 1, 1958 

3. A BURNER FOR MIXING FUEL GAS AND OXYGEN CONTAINING GAS AND BURNING SAID FUEL GAS IN HEATING RELATION TO A FURNACE CHAMBER, COMPRISING, IN COMBINATION, A BURNER HOUSING CONSTRUCTED TO BE MOUNTABLE IN SAID FURNACE CHAMBER, OXYGEN CONTAINING GAS CONDUIT MEANS MOUNTED IN SAID HOUSING AND EXTENDING THERETHROUGH AND CONSTRUCTED TO RECEIVE OXYGEN CONTAINING GAS IN AN INLET PORTION AND WHEN MOUNTED IN HEATING RELATION TO SAID FURNACE CHAMBER DISCHARGE A PORTION OF SAID OXYGEN CONTAINING GAS INTO SAID FURNACE CHAMBER FROM AN OUTLET END PORTION FOR SECONDARY COMBUSTION, WALL MEANS POSITIONED BETWEEN SAID HOUSING AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS UPSTREAM FROM SAID OUTLET END PORTION OF SAID OXYGEN CONTAINING GAS CONDUIT MEANS AND FORMING WITH SAID HOUSING AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS A RECESSED PRIMARY COMBUSTION CHAMBER WITH THE OUTLET THEREOF AT SAID OUTLET END PORTION OF SAID OXYGEN CONTAINING GAS CONDUIT MEANS, SAID PRIMARY COMBUSTION CHAMBER BEING FREE OF FLUID FLOW CONSTRICTION BETWEEN THE INLET AND SAID OUTLET THEREOF, PORTS IN SAID WALL MEANS, SECOND WALL MEANS POSITIONED BETWEEN SAID HOUSING AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS UPSTREAM OF SAID FIRST-NAMED WALL MEANS AND DEFINING WITH SAID FIRSTNAMED WALL MEANS, SAID HOUSING AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS, AN AIR CHAMBER, A PASSAGEWAY BETWEEN SAID OXYGEN CONTAINING GAS CONDUIT MEANS AND SAID AIR CHAMBER, VALVE MEANS MOUNTED RELATIVE TO SAID OXYGEN CONTAINING GAS CONDUIT MEANS POSITIONED AND OPERABLE TO VARY THE SIZE OF SAID PASSAGEWAY BETWEEN SAID AIR CHAMBER AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS, THIRD WALL MEANS BETWEEN SAID HOUSING AND SAID AIR CONDUIT MEANS POSITIONED UPSTREAM OF SECOND WALL MEANS AND DEFINING WITH SAID SECOND WALL MEANS, SAID HOUSING AND SAID OXYGEN CONTAINING GAS CONDUIT MEANS, GAS MANIFOLD MEANS, SAID SECOND WALL MEANS HAVING MEANS THEREWITH IN COMMUNICATION WITH SAID GAS MANIFOLD MEANS TO PASS FUEL GAS THERETHROUGH TO SAID AIR CHAMBER TO BE DELIVERED TO SAID PRIMARY COMBUSTION CHAMBER THROUGH SAID PORTS IN SAID FIRST-NAMED WALL MEANS, AND MEANS WITH SAID INLET PORTION OF SAID OXYGEN CONTAINING GAS CONDUIT MEANS TO DELIVER OXYGEN CONTAINING GAS THERETO, SAID BURNER BEING CONSTRUCTED AND OPERABLE TO BURN FUEL GAS IN SAID COMBUSTION CHAMBER OF SAID BURNER IN A ZONE THEREIN REMOVED FROM SAID OUTLET OF SAID OXYGEN CONTAINING GAS CONDUIT MEANS AND TO DISCHARGE PARTIALLY COMBUSTED FUEL GAS INTO SAID FURNACE CHAMBER FOR MIXING WITH SECONDARY OXYGEN CONTAINING GAS AND FURTHER COMBUSTION IN SAID FURNACE CHAMBER. 